Acrosome reaction mammalian sperm

Within an ecotoxicological perspective, mammalian methods cannot be extrapolated automatically to other species. Sperm of teleosts, for example, differs in a few very important aspects from that of mammals. Unlike mammalian sperm it is not motile on ejaculation and attains motility only on contact with water. After activation it only moves for a few minutes (for freshwater fish typically around 1 min). Furthermore it enters the egg via the micropyle rather than through an acrosomal reaction. The first minute after the start of motility is therefore crucial to its success in fertilizing an egg, and even when it is deposited on the egg s surface it still has to move fast enough in the right direction to reach the micropyle. Clearly the fertilizing ability of fish sperm is very dependent on its motility, and any pollutant that decreases this movement may be expected to affect fertilization. 

Allen, C.A. and Green, D P. (1997). The mammalian acrosome reaction gateway to sperm fusion with the oocyte. Bioessays 19 241-247. 

Langlais, J. and Roberts, K.D. (1985). A molecular membrane model of sperm capacitation and the acrosome reaction of mammalian spermatozoa. Gamete Res. 72 183-224. 

Mammalian fertilization is the result of a precisely regulated series of cellular interactions. This process can be divided into a number of component stages, including the following (i) the early events that precede egg fusion, consisting of the preliminary event of sperm capacitation, sperm penetration of the cumulus oophorus, zona pellucida adhesion, initiation and completion of acrosome reactions, penetration of the zona pellucida, egg plasma membrane contact and fusion and (ii) the late events that occur within the egg that consist of sperm nuclear decondensation followed by pronuclear consolidation and syngamy. 

Sperm penetrate the zona pellucida only after completion of the acrosome reaction. A similar process occurs in nonmammalian species, where sperm must penetrate the vitelline coat. In abalone this is accomplished by release of lysin, an acrosomal protein that disperses the vitelline coat by a noncatalytic mechanism (Lewis et al., 1982 Shaw et al., 1993). In contrast, the generally accepted model for mammalian sperm penetration of the zona pellucida is the acrosin hypothesis in which proteolysis of zona pellucida matrix glycoproteins by acrosin, the acrosomal serine esterase, plays a trailblazing role in the sperm penetration process (Yanag-... 

Amoult, C., Zeng, Y., and Florman, H.M. (1996a). ZP3-dependent activation of sperm cation channels regulates acrosomal secretion during mammalian fertilization. J. Cell Biol. 754 637-645. Amoult, C., Cardullo, R.A., Lemos, J.R., and Florman, H.M. (1996b). Egg-activation of sperm T-type Ca channels regulates acrosome reactions during mammalian fertilization. Prt>c. Natl. Acad. Sci. 95 13004-13009. 

Kopf, G.S. and Gerton, G.L. (1990). The mattunalian sperm acrosome and the acrosome reaction. In Elements of Mammalian Fertilization. Basic concepts (Wassatman, Ed.), pp. 153-203. CRC Press, Boca Raton, FL. 

Meizel, S. (1984). The importance of hydrolytic enzymes to an exocytotic event, the mammalian sperm acrosome reaction, Biol. Rev, 59 125-157. 

AN INTIMATE BIOCHEMISTRY EGG-REGULATED ACROSOME REACTIONS OF MAMMALIAN SPERM Harvey M. Florman, Christophe Arnoult,... 

In Chapter 7, Florman and coauthors review the mechanisms of egg-regulated acrosome reactions of mammalian sperm. Among the aspects discussed are the nature of primary signal transducers and targets stimulated by binding of acrosome-intact sperm to receptors in the egg zona pellucida. In a detailed presentation, the potential roles of several sperm components including G proteins, cation channels, tyrosine kinases, calcium, and cellular pH are considered. 

Meizel S. 1985. Molecules that initiate or help stimulate the acrosome reaction by their reaction with the mammalian sperm surface. Am J Anat 174 285-302. 

Meizel S. 1997. Amino acid neurotransmitter receptor/chloride chaimels of mammalian sperm and the acrosome reaction. Biol Reprod 56 569-574. 

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